Make sure tests always run in the same order by sorting network type names
Added TEREDO IPv6 network - is_teredo_ipv6
Remove extra "not" in error message
Add ORCHID network

Also refactored the sub building & testing code to handle networks which are
subsets of other networks. There are a bunch of these under the IPv6 special
block.
Removed extra =cut and =pod directives
Remove extra (and wrong) =item directives
2001:: and 2001::1234 are not part of the ORCHID network
Add IPv6 documentation network
Sort has of IPv6 networks by network address
Add IPv4-mapped IPv6 network - is_ipv4_mapped_ipv6
Add IPv6 discard prefix network - is_discard_ipv6()